1. Field of the Invention
The present invention relates to a fuel injection valve device for use in, for example, automobile engines and, more particularly, to a fuel injection valve device provided with a nozzle hole plate for atomization of fuel.
2. Description of Related Arts
Under the recent trend of tightening the regulations of exhaust gas, in the field of fuel injection valve device for use in automobile engines, it has been increasingly demanded to improve fuel spray characteristics. To cope with this demand, several attempts of fuel injection valve device have been proposed. In those known fuel injection valve devices, a nozzle hole plate having a plurality of nozzle holes on the downstream side of a valve member consisting of a valve disc and a valve seat is disposed so that atomized fuel is injected from every nozzle hole into each cylinder head of an engine.
For example, the Japanese Patent Publication (unexamined) No. 2004-169572 discloses a fuel injection valve device in which a first nozzle hole plate having vertical cylindrical holes is joined by welding on the tip (downstream side) of the valve member, and a second nozzle hole plate having an inclined cylindrical holes that are larger hole diameter than the mentioned vertical cylindrical holes and communicate with the cylindrical holes of the mentioned first nozzle hole plate is further welded in a superimposed manner on the downstream side of the mentioned first nozzle hole plate, thereby atomization of fuel being carried out.
The Japanese Patent Publication (unexamined) No. 2003-206828 discloses another fuel injection valve device provided with a valve seat for discharging or interrupting the fuel from the injector by engaging or disengaging with a valve seat moving up and down; and a nozzle plate (nozzle hole plate) having a plurality of orifices directly welded and fixed onto the valve seat on the downstream side; and in which the mentioned orifices are shaped into a circular corn spreading toward the downstream side; thereby atomization of fuel and improvement in quality of exhaust gas being achieved.
The Japanese Patent Publication (unexamined) No. 317607/1997 discloses a further fuel injection valve device in which a nozzle plate (nozzle hole plate) is cup-shaped, and a protruding face of a bottom part of this nozzle plate is welded onto a sleeve fixed to a valve member side so as to press the protruding face on the end face of an opening of the valve member, thereby it being avoided to directly fixing the nozzle hole plate to the valve member in order to suppress deflection produced on the bottom part of the mentioned nozzle plate due to fuel injection pressure.